How to isolate machine using iptables and cgroups in ubuntu

Mahe

6/18/24, 4:26 PM

I am trying to isolate a computer from the network. I am running the following commands in linux:

#create net_cls folder for cgroup
mkdir /sys/fs/cgroup/net_cls

#mount the newly created folder 
mount -t cgroup -o net_cls none /sys/fs/cgroup/net_cls

#create new cgroup
cgcreate -g net_cls:/block_app

#add firefox process which is currently running to the group
cgclassify -g net_cls:/block_app $(pgrep firefox)`

#change read/write permissions for the file
chmod 777 /sys/fs/cgroup/net_cls/block_app/net_cls.classid

#assign group id 
echo 1 > /sys/fs/cgroup/net_cls/block_app/net_cls.classid

#add iptable entry to permit firefox process which was added to cgroup 
iptables -I OUTPUT -m cgroup --cgroup 1 -j ACCEPT

#drop all packets
iptables -A OUTPUT -j DROP

Now performing these steps works in my local VM. Local VM settings as follows:

OS: Linux mint 21.1

The same doesn't work in another server running Ubuntu 20.04. It just blocks all traffic including firefox which was added as exception.

I am a novice with managing linux systems. So any pointers or even alternative approaches are welcome.

0 + 0

iptables

firewall

mint

cgroup

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